In hip replacement surgery, a prosthesis is connected to the femur via cement or other adhesive material provided in the femoral canal. In hip replacement surgery in which a previously insert prosthesis is replaced (e.g., because the cement or adhesive has become weak), it is necessary to remove at least a part of the original cement or adhesive from the femoral canal. Loose fragments of the original cement or adhesive must be completely removed. Accordingly, at least some rechannelization of the femoral canal is necessary, and at least some reaming out of the old cement or adhesive is necessary to accommodate the new prosthesis. When reaming out the old cement or adhesive, it is essential that no damage be done to the canal or femoral shaft, since perforations may prevent adequate fixation of the new prosthesis or weaken the femur. Consequently, during the reaming operation, a guide device is needed so that the drill or other cutting element does not deviate from the drilling or cutting path, thereby preventing perforation or other trauma to the bone.
The following are examples of different alignment devices known in the art.
U.S. Pat. No. 4,860,737 to Davey et al discloses a drill alignment apparatus which includes a housing handle having a drill shaft which extends therefrom along an axis, an alignment rod which is parallel to the drill shaft, and an alignment rod support which is connected between one end of the alignment rod and the housing handle. The Davey et al apparatus further includes a clamp having apertures for receiving the alignment rod. The clamp further includes "tines" for engaging the femur.
As indicated above, Davey et al discloses the use of "tines" for engaging the femur, and also discloses that a set or inventory tines be provided to accommodate various bone sizes. The "tines" disclosed in Davey et al correspond to a plate or a set of plates each having tines separated by varying distances. In this regard, the Davey et al apparatus is similar to the so-called "Charnley guide". In Davey et al, the tines of the set of plates vary to accommodate varying widths of bones. However, two disadvantages are attendant with the Davey et al and the so-called "Charnely guide". First, a relatively large inventory of different-sized plates are required in order to accommodate the various sizes of bones. Second, while a plate can be selected from the inventory of different plates for a particular bone, the selected plate usually does not provide a tight grip of the bone, thereby requiring the surgeon to constantly hold the plate against the bone so that the dill bit does not slip off of the bone or bounce off the hard cement and perforate softer surrounding bone.
Great Britain Patent No. 1,448,111 to Crabbe discloses a device for fixing bone fractures. Specifically, Crabbe discloses a device used to guide a pin for neck fractures of the femur. The device includes an L-shaped rod or tube having a sleeve for receiving a tubular shaft and a clamp having an arcuate section adapted to engage the head of a femoral neck. The Crabbe device is not suited to guide a drill to ream out the medullary canal or shaft.
U.S. Pat. No. 4,896,663 to Vandewalls discloses a femoral drill jig including a clamping mechanism including an operating arm, and a cross beam. The jig is used to center a cup over the ball of the femur, which is a procedure seldom used anymore.
U.S. Pat. No. 4,364,381 to Sher et al discloses a surgical clamp and drill-guide instrument including a C-clamp having a curved lower portion, an upright post, and an upper vice arm which extends from a central body portion located on the upright post. The instrument is used exclusively in the jaw for postioning dental implants.
U.S. Pat. Nos. 2,181,746 and 3,945,377 disclose bone clamps/drill guide devices which employ scissor-like clamps.
U.S. Pat. No. 4,502,475 to Weigle et al discloses a drill guide and clamping apparatus including an adjustable scissor-like assembly. The apparatus is used to align screw holes in plates used to fix broken fractured bones.